This invention relates to coiled spring assembly and particularly to one adapted for use with motor vehicle seat belt retractors as a belt rewind spring.
Seat belt retractors are used in all types of motor vehicles to store seat belt webbing which is a part of the occupant protection system of the vehicle. Retractors employ a rewind spring assembly which causes the belt to be withdrawn into the retractor and rolled onto the retractor spool. The rewind spring assemblies typically used with retractors are comprised of a spring cap which retains a coiled steel strip spring. The spring has an outer end which engages the spring cap and an inner end which engages the rotating retractor spool shaft. Many types of existing rewind spring assemblies employ a spring cap which defines a small pocket which communicates with the interior of the cap by an aperture. The radially outer end of the spring has a bent over hook shaped end which engages the end pocket. While such spring assemblies operate successfully, they are relatively inefficient since, when the spring is wound tighly around the center shaft, the outer radial end of the spring is permitted to pivot in the end pocket which results in non-uniform stress levels on the spring. Optimal efficiency of a spring is achieved when the entire steering is subjected to a uniform stress level. As a means of increasing the efficiency of rewind spring assemblies, some retractor manufacturers have adopted spring cap designs which provide a so-called "bridling" effect. By designing the spring end retaining pocket of the spring cap such that a bending load is imposed on the spring end which urges the end of the spring to be forced toward the inside cylindrical surface of the spring cap, the efficiency of the spring can be increased. Enhanced efficiency of the spring permits shorter and lighter spring materials to be used, thereby providing savings in terms of component cost and also reducing the weight and size of the rewind spring assembly. Although it is currently known to provide a retractor rewind spring featuring the bridling effect, the processes now used to fabricate such rewind spring assemblies are very labor intensive and therefore costly, thereby detracting from the advantages of providing the bridling effect. Moreover, current designs of spring assemblies which provide the bridling effect require different spring caps depending on the rotational direction that the spring is wrapped therein.
In view of the foregoing, it is an object of this invention to provide an improved rewind spring assembly particularly adapted for use with seat belt retractors which produces the bridling effect but which can be assembled and manufactured at a minimum of cost. It is a further object of this invention to provide a spring cap which is adapted for rewind springs to be installed therein which are wrapped in either of the rotational directions.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.